Construction of TiO2 nanotube array films modified with ultra-small BiOI nanoparticles and their photocatalytic oxidation activity

BiOI/TiO₂ heterojunction films were prepared on the surface of titanium wire mesh by anodic oxidation combined with a modified successive ionic layer adsorption and reaction (SILAR) method. The absorption of visible light and even near-infrared light by the films was significantly enhanced, and the optical bandgap values of the films were correspondingly reduced to varying degrees. Results from photoelectric current tests, electrochemical impedance spectroscopy, and photoluminescence spectroscopy showed that the formation of the BiOI/TiO₂ heterojunction not only greatly improved the absorption and utilization of solar light, promoted the separation and transfer of photogenerated charge carriers, but also effectively inhibited the recombination of photogenerated charge carriers. Photocatalytic degradation tests of RhB dye indicated that the formation of the BiOI/TiO₂ heterojunction enhanced the performance of the TiO₂ nanotube array films by up to tenfold. In this process, photogenerated holes and superoxide radicals played the most important roles. The BiOI/TiO₂ heterojunction films could also efficiently degrade ethylene gas. In our self-made photocatalytic ethylene degradation system, the films could degrade approximately 87 % of ethylene with an initial concentration of 15 ppm within 600 min. The final degradation products included CO₂.